In order to achieve the object of guiding the valve member of a gate valve during upward and downward movement and to bring it into exact engagement with the seating rings it is necessary for the wedge guide to resist the flow forces acting on the valve member. In the case of gate valves, which do not have any external stop block it is furthermore necessary for the torque of the spindle to be taken up by the wedge guide.
In most cases the wedge guide is permanently connected with the housing wall and it is then either in the form of a welded on bar or in the form of a machined groove or a bar, that is to say the material of the wedge guide is the same as that of the housing. The materials utilized for the housing are however generally only able to withstand very low surface stresses. In the case of gate valves however very high surface stresses frequently occur at the wedge guides dependent on the rated width and the stress differential. Many different forms of damage therefore occur, that in the case of housings welded into pipelines is very difficult to repair. This is something directly affecting the functional reliability of such a gate valve.
The German patent 2,113,415 discloses a wedge guide mounted in a gate valve housing but which however is designed for cooperation with a valve member having parallel walls and sliding on the flat walls of the wedge guide. This wedge consisting essentially of two plates slipped over the seat rings of the gate valve is not suitable for a valve member with a wedge-like outline and for a guiding action using guide bars.
One object of the present invention is to provide a replaceable wedge guide of the type equipped with guide bars, which may be quickly and simply fitted and removed.